The formation of foam in the oil power unit, often caused by a malfunction of the air/oil heat exchanger, represents one of the most common and dangerous issues in hydraulic power units, including those used in wind turbines. This situation is exacerbated by the presence of water mixed or emulsified in the oil, leading to a series of harmful consequences.
Problems caused by foam
- Thermal stress and oxidation: The presence of water in the oil reduces the effectiveness of the lubrication film, causing thermal stress and accelerated oxidation.
- Overheating of components: Inefficient lubrication leads to overheating of mechanical parts, severely damaging them.
- Malfunction of electronic components: Foam and air in the oil can cause problems for electronic components, such as servo-electro-valves.
Causes of foam formation
The main cause of foam formation is the dew effect, where water penetrates the hydraulic power unit due to the temperature difference between the oil and the external environment (ΔT). Emulsified water reduces the viscosity of the oil, facilitating the formation of iron sludge and increasing the presence of air within the power unit.
Solutions to prevent foam
- Proper oil level: It is essential to maintain an optimal oil level to ensure that the gears are fully immersed, avoiding splashes and foam formation.
- Visual and float level switch: Use a visual and/or float level switch with an electric-acoustic signal to monitor the oil level.
- High-quality filters and sensors: Install high-quality filters in suction, delivery, and return, along with a particle counter and a moisture detection probe to monitor oil quality.
- Hydraulic circuit maintenance: Perform regular analyses and maintenance of the hydraulic circuit to ensure consistent and lasting lubrication of internal components.
Use of dehydrators for fluid conditioning
When contaminant levels exceed ISO 4406, NAS 1638, SAE AS 4059 standards, it is advisable to use a mobile dehydration unit. Dehydrators like Pall Corporation’s HNP006 or HNP023 can filter sludge and evaporate water without altering the chemical, physical, and mechanical properties of the oil. This process reduces maintenance costs and prolongs the life of the power unit components.
Preventing foam formation in hydraulic power units requires careful maintenance and the use of appropriate tools to monitor and improve oil quality. Implementing these solutions will help ensure efficient lubrication, reducing the risk of damage and extending the life of the components.
Contact us now to discover how we can help you keep your systems in perfect condition.
